1. Field of the Invention
The invention relates to a pressure or pressure difference measuring instrument comprising at least one diaphragm which is adapted to be responsive to a pressure or a pressure difference and which is connected by a connecting member to a displacement member, the latter member being arranged in a first plane parallel to the plane of the diaphragm and being swingable about a pivot axis which lies in the first plane and is removed from the connecting element.
2. Description of the Prior Art
In one known pressure difference measuring instrument of the above type, the diaphragm which is responsive to the pressure difference is connected via a plunger to a displacement member having the form of a transmission lever. The plunger is connected by welding, for example, to the diaphragm in the plane of the diaphragm. The plunger is also welded to the transmission lever, which is held at one end by a leaf spring supported in the housing of the instrument and executes with its other end a swinging movement corresponding to the difference pressure being measured. Difficulties can arise with the aforesaid pressure measuring instrument in connection with the diaphragm thereof, as due to the construction of the instrument, the diaphragm is deflected asymmetrically by the plunger when the transmission lever swings and is thereby heavily stressed at individual points.
In another known pressure difference measuring instrument, two diaphragms acted upon, respectively, by a higher and a lower pressure are each connected, via respective connecting elements to a resilient bendable tubular member acting as a measuring spring and into which is inserted a rotatable control rod. The control rod executes a swinging movement about a fictitious pivot point under the influence of a pressure difference, the diaphragms being deflected nonuniformly because of the rigid connection between the resilient tubular member and the diaphragms. This type of deflection causes an overload in individual zones of the diaphragms and leads to premature contact of the diaphragms with their respective backings, if the spacing between the diaphragms and the backings is small.
It is an object of the present invention to provide a pressure or pressure difference measuring apparatus with at least one diaphragm adapted to be responsive to a pressure or a pressure difference and in which nonuniform deflection of the diaphragm when the displacement member of the instrument is swung is avoided in a simple reliable manner.